1. Field of the Invention
The present invention relates to a manufacturing method for a wood board, and more particularly, to a manufacturing method for a wood board which provides a wood board of sufficient strength in which there is little warping and a high degree of dimensional stability, the production process therefor being simpler and requiring less time and expense.
2. Background Art
The insufficiency of lumber resources and the conservation of forests have become problematic in recent years, and it is clear that it will become increasingly difficult to obtain timber from forests. Accordingly, the supply of board materials such as plywood, which are produced using large amounts of raw lumber, will become unstable or insufficient, with the cost thereof also expected to rise greatly. Thus, wood boards which can be obtained from the efficient use of wooden strands or ligneous fibers of wooden pieces, or the like, which were conventionally regarded as waste materials, have attracted attention, and the use of such wood boards in various applications strongly desired.
Among such wood boards, fiber boards formed from ligneous fibers and strand boards formed from wooden strands are known. Commonly, in cases where ligneous fibers or other materials having small dimensions are employed, the wood board which is obtained is uniform, and the surface thereof is smooth; however, the strength and rigidity of the wood board are not sufficient. On the other hand, in the case of strand boards which employ wooden strands, the strands employed are larger than ligneous fibers, so that the strength and density of the obtained board can approach that of natural lumber.
These wood boards are produced by applying binder to a raw material such as ligneous fibers or wooden strands, and subjecting the material to forming and thermal compression molding. However, because the molded material obtained by the conventional molding process had a low water content, a considerable degree of warping could occur after shipping. Accordingly, the dimensional stability of such conventionally manufactured boards was poor, while the quality thereof could not be guaranteed. Therefore, in order to adjust the water content of the obtained wood board, a moisturizing step is necessary to increase the water content by moisturizing the molded material. Various moisturizing methods are available, such as a method wherein the molded material is placed inside an artificial drying chamber or a chamber in which temperature and moisture are regulated; a method wherein the molded material is soaked in water; a method wherein the molded material is coated with water using a sprayer; or a steam injection method for which the present inventors submitted a patent application ("Manufacturing Method for a wood board", Japanese Patent Application, First Publication, Hei. 7-232309). Because strand boards produced as described above have considerable surface irregularity, a smoothing step to smooth the surface of the board by sanding or the like is necessary. Accordingly, a large number of steps and considerable trouble, are involved in the conventional manufacturing methods for wood boards, which necessitates a longer production time and higher costs.
Furthermore, the method of placing the molded material in an artificial drying chamber or a chamber in which temperature and moisture are regulated requires a large space in order to carry out the moisturizing step. In the manufacturing method for a wood board according to Japanese Patent Application, First Publication, Hei 7-232309, after moisturizing the molded material and adjusting the water content once, it is necessary to provide a step in which the water content is lowered by drying the wood board in order to correct plastic deformations which remain inside the wood board. Further, more time is required since the wood boards must be left at room temperature for a long period of one to two weeks in order to stabilize the water content, presenting a hindrance to reducing the required manufacturing time.